Tag Archives: Open Systems Adapter

Recently in my day-to-day activities I encountered a 3172 controller and was reminded of my first such encounter, back in 1992. This got me thinking; 25 years of IBM Mainframe IP connectivity! The IBM 3172 Interconnect Controller allowed LAN-to-Mainframe interconnection and was the pioneering technology allowing IP data off-load activities. Historically Mainframe data transfer operations, namely CCW I/O were dependant on a physical channel, where the 3172 was a stepping stone to the Open Systems Adapter (OSA) card in 1994, quickly superseded by the OSA-2 card in 1995. From a performance viewpoint, the OSA/OSA-2 cards matched maximum ESCON speeds of 17 MB/S.

However, the introduction of the OSA-Express technology in 1999 dramatically increased throughput to ~ 333 MB/S. The OSA-Express technology bypasses CCW channel-based I/O processing, connecting directly to the Self-Timed Inter-connect (STI) bus of Generation 6 (Retrofit to Generation 5) S/390 Mainframes. Data is transferred directly to or from the high speed Mainframe memory OSA-Express adapter I/O port, across the STI bus, with no intervening components or processing to slow down the data interchange. This bus-based I/O, a first for IBM Mainframe computing, significantly increases data transfer speeds, eliminating inefficiencies associated with intermediary components.

Additionally, IBM developed a totally new I/O scheme for the OSA-Express adapter. Queued Direct I/O (QDIO) is a highly optimized data queuing-based data interchange mechanism, leveraging from the message queuing expertise IBM acquired with their multi-platform MQSeries middleware solution. The QDIO-specific S/390 hardware instruction for G5/G6 machines, delivered an application to-OSA signalling scheme capable of handling the high-volume, multimedia data transfer requirements of 21st Century web applications. Where might we be without the 3172 Interconnect Controller and the MQSeries messaging solution?

Since OSA-Express2 the channel types supported have largely remain unchanged:

OSE: Non-QDIO, sets the OSA-Express card to function in non-QDIO mode, bypassing all of the advanced QDIO functions.

OSC: OSA-ICC, available with IBM Mainframes supporting GbE, eliminating the requirement for an external console controller, simplifying HMC and to the z/OS system console access, while introducing TN3270E connectivity.

OSX: (OSA-Express for zBX), provides connectivity and access control to the IntraEnsemble Data Network (IEDN) to the Unified Resource Manager (URM) function.

Returning to my original observation, it’s sometimes hard to reconcile finding a ~25 year old 3172 Controller in a Data Centre environment, preparing for a z14 upgrade! In conjunction with the z14 announcement, OSA-Express6S promised an Ethernet technology refresh for use in the PCIe I/O drawer and continues to be supported by the 16 GBps PCIe Gen3 host bus. The 1000BASE-T Ethernet feature supporting copper connectivity, in addition to 10 Gigabit Ethernet (10 GbE) and Gigabit Ethernet (GbE) for single-mode and multi-mode fibre optic environments. The OSA-Express6S 1000BASE-T feature will be the last generation to support 100 Mbps link speed connections. Future OSA-Express 1000BASE-T features will only support 1 Gbps link speed operation.

Of course, OSA-Express technology exposes the IBM Z Mainframe to the same security challenges as any other server node on the IP network, and as well as talking about Pervasive Encryption with this customer, we also talked about the increased security features of the OSA-Express6S adapter:

OSA-ICC Support for Secure Sockets Layer: when configured as an integrated console controller CHPID type (OSC) on the z14, supports the configuration and enablement of secure connections using the Transport Layer Security (TLS) protocol versions 1.0, 1.1 and 1.2. Server-side authentication is supported using either a self-signed certificate or a customer supplied certificate, which can be signed by a customer-specified certificate authority. The certificates used must have an RSA key length of 2048 bits, and must be signed by using SHA-256. This function support negotiates a cipher suite of AES-128 for the session key.

Virtual Local Area Network (VLAN): takes advantage of the Institute of Electrical and Electronics Engineers (IEEE) 802.q standard for virtual bridged LANs. VLANs allow easier administration of logical groups of stations that communicate as though they were on the same LAN. In the virtualized environment of the IBM Z server, TCP/IP stacks can exist, potentially sharing OSA-Express features. VLAN provides a greater degree of isolation by allowing contact with a server from only the set of stations that comprise the VLAN.

QDIO Data Connection Isolation: provides a mechanism for security regulatory compliance (E.g. HIPPA) for network isolation between the instances that share physical network connectivity, as per installation defined security zone boundaries. A mechanism to isolate a QDIO data connection on an OSA port, by forcing traffic to flow to the external network. This feature safeguards that all communication flows only between an operating system and the external network. This feature is provided with a granularity of implementation flexibility for both the z/VM and z/OS operating systems.

As always, the single-footprint capability of an IBM Z server must be considered. From a base architectural OSA design viewpoint, OSA supports 640 TCP/IP stacks or connections per dedicated CHPID, or 640 total stacks across multiple LPARs using a shared or spanned CHPID. Obviously this allows the IBM Mainframe user to support more Linux images. Of course, this is a very important consideration when considering the latest z13 and z14 servers for Distributed Systems workload consolidation.

In conclusion, never under estimate the value of the OSA-Express adapter in your organization and its role in transitioning the IBM Mainframe from a closed proprietary environment in the early 1990’s, to just another node on the IP network, from the mid-1990’s to the present day. As per any other major technology for the IBM Z server, the OSA-Express adapter has evolved to provide the requisite capacity, performance, resilience and security attributes expected for an Enterprise Class workload. Finally, let’s not lose sight of the technology commonality associated with OSA-Express and Crypto Express adapters; clearly, fundamental building blocks of Pervasive Encryption…